My own writing tends to flow very much from the voices of the characters, which has led to some pitfalls with attempts at plotting, particularly at the points where Character X needs to perform Action Y or everything that should follow to allow an orderly progression to the climax of the story doesn't, and I realize that, well, Mr. X would never do that.

And then what?

Figure out a new way, a different character, a different action that moves the plot along? Figure out a new plot? Figure out that Mr. X has been lying to you all this time, and perhaps even to himself, and that in a critical time of stress, yes, he would do the thing the plot requires of him, and spend the rest of the novel trying to sort out why? Why didn't I try to save that kid from drowning? Or, depending on the character - Why did I risk my life saving that stupid kid from drowning?